U.S. Attorney Peter Neronha says in a letter delivered to Chafee on Friday that federal prosecutors have the right to investigate and prosecute those who grow and distribute marijuana, even if such activities are allowed by state law.

The state announced last month that it had picked three organizations to serve as state-regulated dispensaries for medical pot. Before they can serve patients, the compassion centers must pass a state inspection and receive local occupancy permits. Qualified patients will then be allowed to designate one of the centers as their authorized source of marijuana.